The present invention relates to a magnetoresistive effect (MR) element used as a magnetic sensor, a thin-film magnetic head with the MR element and a manufacturing method of the MR element. The present invention particularly relates to a MR element of a thin-film magnetic head for hard disk drive units, and to a manufacturing method of the MR element.
Recently, thin-film magnetic heads based on spin valve effect of giant magnetoresistive characteristics (GMR) are proposed as magnetic heads with high sensitivity and high output in order to satisfy the requirement for ever increasing data storage densities in today""s magnetic storage systems such as hard disk drive units.
The spin valve effect thin-film structure includes first and second thin-film layers of a ferromagnetic material separated by a thin-film layer of non-magnetic material, and an adjacent layer of anti-ferromagnetic material is formed in physical contact with the second ferromagnetic layer to provide exchange bias magnetic field by exchange coupling at the interface of the layers. The magnetization direction in the second ferromagnetic layer is constrained or maintained by the exchange coupling, hereinafter the second layer is called xe2x80x9cpinned layerxe2x80x9d. On the other hand the magnetization direction of the first ferromagnetic layer is free to rotate in response to an externally applied magnetic field, hereinafter the first layer is called xe2x80x9cfree layerxe2x80x9d. The direction of the magnetization in the free layer changes between parallel and anti-parallel against the direction of the magnetization in the pinned layer, and hence the magneto-resistance greatly changes and giant magneto-resistance characteristics are obtained.
Japanese Patent Unexamined Publication No. 04-358310 discloses a spin valve MR sensor which consists of sequentially stacked layers of a bottom layer, a free layer, a non-magnetic layer, a pinned layer and an anti-ferromagnetic layer on a substrate. In this spin valve MR sensor, all the layers except for the bottom and free layers are partly removed to form a magnetic sensing region corresponding to a track width region in case the sensor is used in a magnetic head. In other words, the free layer that will operate as a magnetic sensor exceeds both ends of the magnetic sensing region or the track width region. Therefore, when this spin valve MR sensor is used in the magnetic head, the magnetic sensor will be overlapped on the neighboring tracks and hence this head structure is not effective in more high dense data sensing.
Japanese Patent Unexamined Publication No. 08-221719 discloses a spin valve MR sensor in which a free layer exists only within the track width region. This type of spin valve MR sensor is fabricated by sequentially stacking on a substrate, a lower shield layer, a shield gap layer of an insulation material and a spin valve multi-layered structure which is constituted by a free layer, a non-magnetic metal layer, a pinned layer and an anti-ferromagnetic layer sequentially stacked from the bottom. Then, a specifically patterned resist layer is formed as a mask on the spin valve multi-layered structure by photo-lithographic technique, and ion milling process is implemented to form a specific shaped magnetic sensor of the spin valve multi-layered structure. Namely, the both end portions of the spin valve multi-layered structure, which exceed the magnetic sensing region, are removed away. After this process, magnetic domain control layers and lead conductor layers are formed.
However, according to this Japanese Patent Unexamined Publication No. 08-221719, over-milling onto the spin valve multi-layered structure is necessary at the ion milling process of this structure in order that incomplete milled part of the structure does not exist in any area of the wafer. Namely, the milling process is to be done extending into the shield gap layer exceeding the spin valve multi-layered structure.
As a result of such ion milling, the released particles of the shield gap layer of insulation material such as Al2O3 are re-deposited on the interface area between the spin valve multi-layered structure, and the magnetic domain control layers and lead conductors to form high electrical resistive residual layers. This results in not only higher electrical resistance of the spin valve MR sensor, but also wider spread of the dispersion in electrical resistance values of such sensors. Furthermore, the over-milling may cause definite degradation of electrical insulation characteristic between the lower shield layer and the spin valve multi-layered structure due to the thinned shield gap layer.
In addition, according to this Japanese Patent Unexamined Publication No. 08-221719, the electrical contact between the spin valve multi-layered structure, and the magnetic domain control layers and the lead conductor layers is only by the cross sectional side interfaces of the patterned spin valve multi-layered structure. More thinly spin valve multi-layered structure and lower height of the stripe from ABS (Air Bearing Surface) or lower MR height result in definite decrease of the electrical contact area and increase of the contact resistance. This increase of the contact resistance may cause shorter life of the sensor due to self-heating and/or electro-migration of the MR sensor. It is possible to enlarge the contact area by making the shape of the cross sectional side interfaces in a greatly tapered shape. However, such shape may invite increase in Barkhousen noise and also increase of the output signal fluctuations.
The above-mentioned problems may be caused not only in such spin valve MR element, but also in an usual anisotropic MR element.
It is therefore an object of the present invention to provide a MR element, a thin-film magnetic head with the MR element and a manufacturing method of the MR element, whereby electric resistance at the interface between a spin valve multi-layered structure or other MR multi-layered structure and a magnetic domain control layer and a lead conductor layer becomes low and its dispersion can exist in a narrow range.
Another object of the present invention is to provide a MR element, a thin-film magnetic head with the MR element and a manufacturing method of the MR element, whereby electrical contact area at the interface between a spin valve multi-layered structure or other MR multi-layered structure and a magnetic domain control layer and a lead conductor layer becomes more larger.
According to the present invention, a MR element, with a magnetic sensing region and outside regions thereof which locate outside the magnetic sensing region along a track width direction, includes a multi-layered structure with an anti-ferromagnetic thin-film layer, a first ferromagnetic thin-film layer constituted by a single layer of ferromagnetic material or by multi layers of ferromagnetic material, a non-magnetic metal thin-film layer and a second ferromagnetic thin-film layer constituted by a single layer of ferromagnetic material or by multi layers of ferromagnetic material which are sequentially formed on a substrate. The all layers in the multi-layered structure exist in the magnetic sensing region, and at least the anti-ferromagnetic thin-film layer with its initial thickness exists in the outside regions.
In this multi-layered structure, the second ferromagnetic thin-film layer (free layer) is formed in the opposite (upper) side of the substrate, and at least the anti-ferromagnetic thin-film layer with the initial thickness exists in the outside regions of the magnetic sensing region, and hence even when over milling process is implemented to pattern the free layer, an insulation layer under the anti-ferromagnetic thin-film layer is not attacked. Therefore, insulation material particles do not re-deposit on the cross sectional interface area of the spin valve multi-layered structure, the magnetic domain control layers and lead conductor layers, and the interface electrical resistance can become low and its dispersion can be restricted in a narrow range.
Particularly, according to the present invention, at least the anti-ferromagnetic thin-film layer with initial thickness exists in the outside regions of the magnetic sensing region, and therefore re-deposition of particles during the milling process of this anti-ferromagnetic layer is not caused. In general, the resistivity of an anti-ferromagnetic thin-film layer is larger than that of other thin-film layers, and this causes definite increase of the interface resistance when the particles are re-deposited on the interface surface area. When an anti-ferromagnetic thin-film layer is formed of oxide material such as NiO, Fe2O3 or CoO, the interface resistance is usually degraded. By this reason, non re-deposition of particles of anti-ferromagnetic material gives a great advantage.
Furthermore, the electrical contact area between the spin valve multi-layered structure and the magnetic domain control layers and the lead conductor layers includes not only the tapered side areas at the both ends of the spin valve multi-layered structure, but also the interface area between a part of the upper surface of a layer in the spin valve multi-layered structure and the magnetic domain control layers. Thus, the electrical resistance of the spin valve MR element becomes smaller and the life of the element becomes longer.
It is preferred that, in the outside regions, only the anti-ferromagnetic thin-film layer with its initial thickness exists.
It is also preferred that, in the outside regions, only the anti-ferromagnetic thin-film layer with its initial thickness and the first ferromagnetic thin-film layer with its thinned thickness exist.
It is preferred that, in the outside regions, only the anti-ferromagnetic thin-film layer with its initial thickness and the first ferromagnetic thin-film layer with its initial thickness exist.
It is also preferred that, in the outside regions, only the anti-ferromagnetic thin-film layer with its initial thickness, the first ferromagnetic thin-film layer with its initial thickness and the non-magnetic metal thin-film layer with its initial thickness exist.
It is preferred furthermore that, in the outside regions, magnetic domain control layers which are contact with the second ferromagnetic thin-film layer and the lead conductor layers exist.
According to the present invention, also, a MR element with a magnetic sensing region and outside regions thereof which locate outside the magnetic sensing region along a track width direction, includes a multi-layered structure with a soft-magnetic adjacent layer for magnetic biasing constituted by a single layer or multi layers, a non-magnetic layer and a MR layer constituted by a single layer or multi layers which are sequentially formed on a substrate. The all layers in the multi-layered structure exist in the magnetic sensing region, and at least the soft-magnetic adjacent layer with its thinned thickness exists in the outside regions.
The MR layer is formed on the opposite (upper) side of the substrate, and in the outside regions of the magnetic sensing region, at least the soft-magnetic adjacent layer for magnetic biasing of its partial thickness exists. Therefore, even when over milling process is implemented to pattern the MR layer, an insulation layer under the soft-magnetic adjacent layer for magnetic biasing is not attacked. Thus, insulation material particles do not re-deposit on the cross sectional interface areas between the MR multi-layered structure, and the magnetic domain control layers and the lead conductor layers. As a result, the interface electrical resistance can be lowered and its dispersion can be restricted in a narrow range. Also, the electrical contact area between the MR multi-layered structure and the magnetic domain control layers and the lead conductor layers includes not only the tapered side areas at the both ends of the MR multi-layered structure, but also the interface area between a part of the upper surface of a layer in the MR multi-layered structure and the magnetic domain control layers. Thus, the electrical resistance of the MR element becomes smaller and the life of the element becomes longer.
Furthermore, according to the present invention, a method of manufacturing a MR element, with a magnetic sensing region and outside regions thereof which locate outside the magnetic sensing region along a track width direction, the method includes the step of sequentially forming, on a substrate, an anti-ferromagnetic thin-film layer, a first ferromagnetic thin-film layer constituted by a single layer of ferromagnetic material or by multi layers of ferromagnetic material, a non-magnetic metal thin-film layer and a second ferromagnetic thin-film layer constituted by a single layer of ferromagnetic material or by multi layers of ferromagnetic material, and the steps of removing, in the outside regions, the layers except for at least the anti-ferromagnetic thin-film layer with its initial thickness.
It is preferred that the removing step includes the step of removing, in the outside regions, the layers to leave only the anti-ferromagnetic thin-film layer with its initial thickness.
It is also preferred that the removing step includes the step of removing, in the outside regions, the layers to leave only the anti-ferromagnetic thin-film layer with its initial thickness and the first ferromagnetic thin-film layer with its thinned thickness.
It is preferred that the removing step includes the step of removing, in the outside regions, the layers to leave only the anti-ferromagnetic thin-film layer with its initial thickness and the first ferromagnetic thin-film layer with its initial thickness.
It is also preferred that the removing step includes the step of removing, in the outside regions, the layers to leave only the anti-ferromagnetic thin-film layer with its initial thickness, the first ferromagnetic thin-film layer with its initial thickness and the non-magnetic metal thin-film layer with its initial thickness
It is preferred furthermore that the removing step includes the step of executing ion milling the layers in the outside regions.
It is preferred that the method further includes the step of forming magnetic domain control layers which are contact with the second ferromagnetic thin-film layer and lead conductor layers in the outside regions.
Also, according to the present invention, a method of manufacturing a magnetoresistive effect element, with a magnetic sensing region and outside regions thereof which locate outside the magnetic sensing region along a track width direction, includes the step of sequentially forming, on a substrate, a soft-magnetic adjacent layer for magnetic biasing constituted by a single layer or multi layers, a non-magnetic layer and a magnetoresistive effect layer constituted by a single layer or multi layers, and the step of removing, in the outside regions, the layers except for at least the soft-magnetic adjacent layer with its thinned thickness.
The magnetic sensing region or track width region exactly means ABS side region of an upper surface of the second ferromagnetic thin-film layer of the spin valve MR element or an upper surface of the MR layer of the anisotropic MR element, which region is defined by the magnetic domain control layers and the lead conductor layers, and its outside regions along the track width direction mean ABS side regions outside the magnetic sensing region or track width region of the upper surface. However, the side surfaces at the both ends of the MR multi-layered structure are tapered. Thus, the ABS side region between the both sloped end surfaces of the second ferromagnetic thin-film layer or the MR layer is considered as its magnetic sensing or track width region, and the ABS side regions of each layer outside its magnetic sensing or track width region along the track width direction is considered as its outside region along the track width direction.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.